The present invention relates to an air spring, and more particularly to an air spring with an inner airbag as a roll off piston.
Air spring assemblies are utilized for a variety of applications. One such application is to cushion the ride of a vehicle. An air spring assembly generally includes a flexible member attached to a piston. The piston advances or retreats into the interior of the flexible member, which changes the internal volume of the assembly. The spring rate depends on the change of internal volume and the effective area of the piston. In addition, the amount of air delivered to the interior of the flexible member is adjustable to vary the preload or ride height.
To vary the spring rate of a conventional air spring, auxiliary air tanks are selectively connected to the flexible member to change the effective volume of the air spring. Disadvantageously, the auxiliary air tanks may present packaging difficulties and are limited by the cross-sectional area of the flow path between the air spring and the auxiliary air tank. Such an arrangement limits the air spring to a two-stage spring rate in which either the auxiliary air tank is connected or disconnected.
Accordingly, it is desirable to provide an air spring assembly, which achieves variable spring rates without auxiliary air tanks.